Medical devices for performing surgical operations through an endoscope are known. For example, Japanese Unexamined Patent Application, First Publication No. H10-234743A discloses a high-frequency excision tool which can be combined with an endoscope. In addition, Japanese Unexamined Patent Application, First Publication No. 2010-178766A discloses an endoscope for treatment which can be combined with a high-frequency snare device which incises tissues by applying a high-frequency current thereto. The endoscope for treatment disclosed in Japanese Unexamined Patent Application, First Publication No. 2010-178766A has an engaging part to which the loop portion of the high-frequency snare device can be caught at a distal end, and is configured to excise entire layers of a wall of a body object using a wire portion of the high-frequency snare device positioned at more proximal than the loop portion as an incision electrode.